To compare the performance of the main methods used to estimate stone burden in order to improve and standardize preoperative evaluation of stone disease.
From January 2012 to June 2013, a series of consecutive retrograde intrarenal stone surgery was prospectively evaluated at a single institute.
All patients had a pre- and postoperative CT scan The stone burden was estimated using 3 methods: the cumulative stone diameter (M1), Ackermann's formula (M2), and the sphere formula (M3) The predictive value of the postoperative stone-free status of these methods was then compared
Overall (n = 142), the stone-free rate was 64% The three methods (M1, M2, and M3) were all predictive of stone-free status for stones 20 mm (P = 0024 and 023) Using receiver operating characteristic curves, we found that areas under the curve were 0 73, 0 70, and 0 71 for stones below 20 mm and 0 53, 0 74, and 0 74 for stones above 20 mm for M1, M2, and M3, respectively In multivariate analysis, M1 and M3 were both found to be independently associated with the stone-free status in the whole series (P < 001 and 011, respectively) However, for stones above 20 mm, only M3 was significant (P = 020)
Evaluation of the stone burden is an important predictor of the outcome of retrograde intrarenal stone surgery For stones below 20 mm, all the three methods approximate stone burden correctly; however, for the stones above 20 mm, calculation of volume is recommended
Urology 2015 Jun 30 [Epub ahead of print]
Olivier Merigot de Treigny, Elie Bou Nasr, Thierry Almont, Ivan Tack, Pascal Rischmann, Michel Soulié, Eric Huyghe
Hôpital Rangueil University Medical Center, Toulouse, France , Hôpital Rangueil University Medical Center, Toulouse, France , Hôpital Rangueil University Medical Center, Toulouse, France , Hôpital Rangueil University Medical Center, Toulouse, France , Hôpital Rangueil University Medical Center, Toulouse, France , Hôpital Rangueil University Medical Center, Toulouse, France , Hôpital Rangueil University Medical Center, Toulouse, France